Automatic telephone selecting system



W. T. POWELL;

AUTOMATIC TELEPHONE SELECTING SYSTEM. APPLICATION FILED JAN. 24. I919.

Patented Oct. 17, 1922 IEHII- MARGINAL INVENTOR WTNF ED T. POWELL.

ATTORNEY Patented Get. 17, R922.

entrain stares WINFRED T. POWELL, ROCHESTER, NEW] YQR-K, ASSIGNOR TO THESTRUT/[BERG- GARLSON TELEPHONE MANUFACTURING COh IPANY, ROCHESTER, NEWYORK,

A CORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE SELECTING SYSTEM.

Application filed January 24, 1919. Serial No. 272,955.

T 0 (all 10710-772, it may concern:

Be it known that I, lViNrRnn T. PownLL, citizen of the United States,residing in Rochester, in the county of Monroe and State of New York,have invented certain new and useful Improvements in Automatic TelephoneSelecting Systems, of which the following is a full, clear, concise, andexact description.

My invention relates to telephone systems, and more particularly to suchsystems as are well-known in the art as automatic telephone systems,wherein any one of a number of subscribers to the system may without themanual. aid of an operator, operate the central station switchingapparatus under the control of the subscriber substation apparatus tointerconnect the calling subscribers line with adesired one of the othersubscribers lines.

An object of my invention is to provid an improved organism for such asystem as will attain great efficiency of operation with the minimum offailures, this being accomplished with a relatively small amount ofapparatus operating in a most positive manner.

It is a further object of my invention to provide a novel means ofcontrolling the movements and release of the switch mechanism employedin interconecting the lines; other objects of my invention and theinvention itself will be made apparent from the description of the samewhich follows, and in which description reference is made to theaccompanying drawing showing a preferred embodiment of my invention.

Referring to the drawing, at A and B I show two telephone substationscomprising talking and signalling apparatus, as will be later more fullydescribed herein, these substations being connected by telephone linesto main station apparatus individual to each of the lines; this mainstation line apparatus being shown at L for the calling line station A,and at M for the called line station B. I

It will be understood that either of these stations might be the callingor called station, but for convenience in this description, it will beassumed that the calling station A is seeking a connection with a calledstation B; other telephone lines for other stations would of course beprovided for such a system as herein'described.

At ON, I show a telephone line interconnecting circuit consisting of adirectively operated numerical switch mechanism, not shown in detail butwhich may be. of any of the well-known forms of switch mechanismcommonly used in the art to which this invention appertains, and it willbe assumed in this description that the switch mechanism is of the typewhose outgoing wipers, by which connection is made to a desired calledline, are moved first in a primary direction under the control ofcalling substation apparatus, and thereafter moved in a secondarydirection under subsequent control by the calling substation apparatus.Other equivalent forms of switching mechanism are contemplated.

through the terminals of a called line which comprise contactsassociated with the called line adapted to be engaged by the travelingswitch wipers of the switch mechanism CN.

The substation A comprises a transmitter t, adapted to be energized bycurrent flowing over the line from the central station, a receiver 1',an induction coil 2', together with the usual telephone bell andserially connected condenser illustrated by the usual symbols, switchhook contacts '8 adapted to control the connection of the substationapparatus with the line conductors 1 and 2 of the calling line; alsoincluded at the substation A are contacts 7, 4L5, and 47 of asubscribers selective switch controlling mechanism, comprising the usualform of 2 wire dial.

The controlling mechanism for these contacts is so organized, that whenthe subscriber gives the dial the preliminary forward movement, contact4-5 opens and con tacts 46 and 47 close. The circuit connectionthereupon causes the contacts 46. to

oulse s )rin s 7 are ooened a definite redetermined number of timescorresponding to the digit of the desired line number at the time beingdialed, the operations of the springs 7 being but'momentary andoccurring in rapid succession.

Immediately after the last interruption of the circuit by the contact 7,as described, and prior to the subsequent closure of these contacts,contacts 46 and 47 are opened, and contact 45 is closed to place thesubstation relay C of the substation apparatus in circuit with the line.This relay G contains normal contact 6 in circuit with the contact 7, sothat when the relay C is operatively connected in circuit that the linecurrent over the line will operate the relay C, and

its contact 6 in the circuit of the contact 7 being opened, thesubsequent closure of the contact 7 will be impotent. The relay C is ofrelatively high resistance for a purpose to be made clear in thedescription of the connector switch relays T and R.

At the main station for the line containing the substation A and whichleads by circuit conductors land 2 to the main station, there isprovided a line switch having wipers 17, 24, 4, 14 and 10 which normallyrest upon a set of home passive contacts, a plurality of which arepreferably provided, although a single set willsuflice, Such a pluralityof home passive contact sets will preferably be interposed betweenalternate sets of trunk point passive contacts to each set of whichcircuit conductors leading to the controlling circuits of a connectorswitch mechanism CN will be connected. Such a home point contact setis,for instance, at 16, 23, 3, 13 and 11. A passive set of trunk pointcontacts is shown at 222, 32, 35, 104 and 36, these being connected bycircuit conductors to the connector switch I mechanism CN. Other sets oftrunk' point contacts will be preferably provided for the switch, suchanother set being shown, for instance, as the set containing the contact31. i

The line switch wipers are controlled in their movements by steppingmagnet ST, designated 29, having a reciprocating armature and contacts28. The line relay LR and the cut-off relay CO, for the line, co-operatein the control of this stepping magnet. The

line switch mechanism including the said stopping magnet and relays, isadapted to operate to connect the calling line through the line switchwipers and trunk point switch contacts of such a switch mechanism as UNas may at the time be idle, to the circuits of such a switch mechanism,connec tion being had through the circuit conductors as 33, 34, 38 and37 for the switch mechanism ON.

Associated with the switch mechanism CN, is a primary stepping magnet PMadapted to step the connector switch wipers 57, 58 and 59 in a primarydirection, and a secondary stepping magnet SM to thereafter step thesaid wipers in a secondary direction, whereby connection is made withthe called line terminals, such as the terminals 72, 87 and 80 of thedesired called line. Controlling the operation of the primary andsecondary stepping magnet, is an escape magnet ESC which operates uponeach deenergization to advance the side switch wipers 52, 68, 69, andfrom one operative position to another in thewell known manner, also astep by step switch comprising wipers 43, 41. and 44 and a steppingmagnet MO therefor, also relays T andR which exercises primarily acontrol over the said step by step switch, the escape magnet and theprimary and secondary stepping magnets.

Associated also with the switchmecha nism is a busy test relay BY, aringing trip relay TR, a release magnet REL, a release relay RLcontrolling the said release magnet, and other apparatus and circuitorganizations which will be more fully described in the narrative of theoperation of the system which will later follow.

For a plurality of switch mechanisms, as ON, there, is provided a timingcircuit controlling, means, consisting in the embodi- ,ment illustrated,of a pair of rotary commutators 121 and 122 mounted on a shaft,

113, which is continuously rotated to cause the successive operation ofthe contacts 92 and 93 by the said commutators, the commutators bemg soorganized as to provide a definite time interval between successiveoperations of the twocontact sets 92 and 93 respectively.

A ringing source of current and auxiliary apparatus, common to aplurality of switch mechanisms, is shown as a ringing generator GN, aninterrupter INT, and a resistance lamp LP. A. source of busy tonecurrent BZ, common to a plurality of switch mechanisms, is alsoindicated in the drawing.

lVhereas aplurality of sources of operating current is shown in thedrawing for the purpose of simplifying the same, it will be understoodif desired only a single source of such a continuous source of currentmay be used, the'various circuit conductors leading to the two poles ofthe various illustrated sources then being multiply connected to the twopoles of a singlesource, Thus having therefore set forth the variousoperative parts of the system of my invention, a narrative of a sampleoperation of the same will now be had to better describe the functionsto the second row of terminals.

of the various parts and of the results achieved by the co-operativeaction of the various elements.

In this narrative of operation it will be assumed that the substation Ais the calling substation and the substation B is the called one of aplurality of other substations, and the description will be made withthe assumption that the called line is idle and a connection thereforehad with the called line, and also description of the system as operatedwhen the called line is busy will be had.

The subscriber at substation A, upon removing his receiver 9", closes acircuit to operate the line relay LR of line switch L as follows: groundG, terminal 3 and wiper 4 of line switch L, contact 5 of cut off relayCO, line conductor 2, contact 6 of, relay (1 at substation A, impulsecontact 7, transmitter 2?, switch hook contact 8, induction coil 2',line conductor 1, contact 9 of relay CO, line switch wiper 10 andterminal 11 thereof, winding of line relay LR to the source of current.The line relay Llt'operates and closes the following circuit to operatethe line switch cut off relay CO z-ground GA, contact 12 of relay LR,terminal 13 and line switch wiper 14, winding 15 of relay CO to thesource of current. This ground GA also is extended, from wiper 14 by wayof terminal 16 and line switch wiper 17, to connector terminal 18, whichpath causes the calling line to test busy to incoming calls the instantthe line relay LR operates. The cut off relay CO operates over thepreviously traced circuit and breaks the original circuit of relay LR atcontacts 5 and 9. Before this circuitis broken, a substitute circuit isprovided for relay LR at its own contacts 19 and 21 and thecontact ofrelay CO. A circuit is now closed for operating the line switch steppingmagnet ST as follows z-ground GA, contact 22 of relay LR, terminal 23and line switch wiper 24, contact 25 of relay CO, contact 28 and winding29 of stepping magnet ST to the source of current. The mag net STenergizes its armature, breaks its own circuit at contact 28. and, uponretracting its armature, moves the wipers 4, 10, 1.4, 17 and 24 onestep, i. e., from the first Wiper 14 breaks the original circuit forrelay CO but, assuming the trunk to which the second row of terminalsleads to be busy, this relay does not release because of the followinglocking circuit rground GB, contact 26 of a relay like CO, wiper 24 andterminal 81 of a line switch like L which is using this trunk, by way ofthe line switch bank multiple to terminal 31 of this calling line switchL, wiper 24, contact 27 of relay CO, winding of relay CO to, the sourceof current. This busying ground .also causes the stepping .the impulsesbeing sent.

magnet ST to operate byway of contact 25 of relay CO .and go to thethird row of terminals from which point it will be advanced in the samemanner as described for the first row.

' As long as the'line switch wipers are, away from their home points andon a. trunk point, ground GC is extended by way of wiper 17 to theconnector terminal 18, to cause the line to test busy.

- The cut off relayCO now releases, because there is noground on eitherwinding, and extends the line conductors 1 and 2 to. the connector CN byway of contacts 5 and 9 and line switch wipers 4 and 10. Groundconnection GB is now extended through con tact 26 of relay CO, wiper 24and terminal 32 of line switch L, to trunk wire 33 leading to theconnector CN, for busying this trunk and thereby causing other lineswitches like L to pass over this multiple on their banks. The relay CO,upon releasing,

breaks the circuit of relay LR at contact 20 which allows LE- torelease.

The closed circuit of the calling line is new extended to the connectorCN and causes relays T and R to operate over the following circuit:-ground GD, winding of relay T, connector trunk wire 34, terminal 2-35and wiper 4 of line switch L, contact 5 of relay CO, line conductor 2,previously traced closed circuit of substation A, line conductor 1,contact 9 of relay CO, wiper 1O and'terminal 36 of line switch L,connector trunk wire 37, winding of relay R to the source of current.Both relays T and 13 now energize R closing the following circuit:-ground GE, contact 39 of relay R, terminal 40. and wiper 41 ofchange-over switch CHO, contact 42 and winding of change-over switchstepping magnet M0 to the source of current. Mag net MO now energizes,breaks its own circuit at contact 42, retracts its armature and moveswipers 41, 43 and 44 in a clock-wise direction to the second set ofterminals.

Assuming the subscriber at substation A to be calling the subscriber atsubstation B, lBs number being20; as the calling device is pulledforward contact 45 opens and contacts 46 and 47 close, 46 shortcircuitingthe transmitter t to eliminate its variable resistance fromtheline circuit during inpulsing and 47 short circuiting the primaryinduction coil 2' so that thecalling subscriber will not hear theobjectionable clicks caused by As-the dial returns, the substationimpulse springs 7 are operated twice (the first digit of the desirednumber being 2) momentarily, each time breaking the circuit of theconnect-or relays T and R, both ofthem releasing. At the first break,relay Rclos'es the following circuit: ground GE, contact 48 of relay R,terminal 49 and wiper 41 of switch CHO, 0011- tact 42 and winding ofmagnet M0 to the" source ofrcurrent. This causes switch CHO to advanceits wipers" 4-1, 43 and tt to the third row of terminals. This sameground GE by way of contact 48 of relay R also extends to wiper i lofswitch CHO, terminals 50,01 51, connector side switch wiper 52,'andfirst position contact thereof, winding of primary magnet PM to thesource of current. The wire to connector side switch v52 is multipled topoints 50, 51 and 53 of switch CHO wiper 44 and is for the pur JOSG ofdelivering the fullimpulse of relay to the connector switch operatingmagnet. To prevent this circuit being interrupted as wiper Mcxmoves fromone point to another,

the wiper. is "made bridging, i. e., it makes connection with thesucceedmgcontact before breaking from the preceding. contact.

2&60

vT operates and, as before,.closes a circuit from ground GD, contact 54:of relay'T, te"r-' minal and wiper ell-of switch CHO, 0011- v a tact 42and winding of magnet MO.

Calling device impulse contact 7 is now closed, whereupon relays T and Renergize, T,.clos1ng. the following c1reuit:'ground GD, contact ofrelayT, terminal 55 and wiper ll of switch. CHO, contact 42 and winding ofstepping magnet MO. This causes wipers MA?) and 4:4: to advance to thefourth set of terminals Where the same circuit again operates magnet MOand moves the wiipers 4:1, 43 and 44- to the fifth set of terminals.Here the following circuit is -ClOSECi :-ground GE, contact 39 of relayR,

terminal 60 and wiper 41 of switch-CHO, contact 42 andv winding ofstepping magnet MU to the source of current. This causes theswitch CHOto advance to the next set of terminals, which is the first, and fromhere the same circuit by way of terminal 10 again steps the wipers .41,43 and tr tothe second set of terminals.

Call ng device contact '7 lSDOWQgEL'HI opened, causingthe same series ofoperations as before, i. e., CHO switch wipers 41,

and 44; will advance to the third row of terminals and another impulsewill be delivered to the connector primary'magnet PM; as previouslydescribed for the first break of contact?- at substation A. Immediatelyafter this second opening of contact 7, contacts 46 and 47 are openedand contact 45 is closed. This places relay C, of

"the substation apparatus, in the line circuit for a sufficient time,before the closure of contact 7, for relay C to operate. 7 Relay C, inoperating, breaks its contact (3 which T5 5 opens the path for the'shortcircuit around its windingplaced there byv the closure of contact 7..Relay C is of suflieiently high resistance .to prevent the operation ofmarginal relay R at the connector CN, but will permit. sensitiverelay Tto operate. Relay This causes CHO switch wipers 4L1, 43 and l i tochange-over advance to the fourth position and here the same circuit byway of terminal 56 causes ing circuit is now closed: ground GF, off

normal contact 66, contact 67 of busy relay BY, connector s1de switchwiper 65 and first position thereof, contact 64- of the escape magnetESC, winding of relay R to the source of current. This causes threethings to happen, first, relay R energizes, second, because of the shortcircuit placed on the calling. line by thi above traced circuit, the

'relay G at substation A releases and short circuits itself, third,relay T tie-energizes and opens the locking circult of the escape magnetESQ, which releases and takes the short circuit off the'line, allowingrelay R to again energize; RelayC does not energize at this time becauseit will be short circuited by the impulse contact '7 and its own contact6, the last" closure of impulse contact 7 having taken place beforethese other functions, which have been described, .had time to occur.

Ftelay R, upon energizing, causes wipers-41,.4l3 and H of switch CHO toadvance to the second setof terminals over the circuit previouslytraced. Magnet ESC, upon tie-energizing, allows the connector sideswitch wipers '52, 65, 68, 9 and-70 to' advance. to the second position.

From the foregoing it .will be seen that,

operations which the different parts perform :Firstconnector seized,changeover switch moved one step. Secondopening of' calling deviceimpulse springs, connector wipers stepped to first level and switchmoved one step. Third-closure of calling device impulse springs,change-over? switch moved four steps, coming to rest on the secondpoint. Fourth-opening ofcalling device impulse springs, connector wipers stepped to second level and change-over switch moved one step.Fifth--closure ofcalling devicecircuit through high resistance coil C,changeover switch moved twosteps, coming to rest on the fifth point;Sixthescape magnet operates, restores the telephone and switch circuitsto the starting point for the second digit, i. e., change-over switch toits second point, side switch wipers in second position and the 2000ohms resistance at telephone short-circuited. Thus it will'be seen thatthe change-over? switch when the calling subscriber. dials the firstdigit, 2, the following is the sequence of CHO makes one complete cycle,coming to rest on the second set of terminals, for each impulse (openingand closure) sent in from the calling device: and after the last impulseof the series has been sent, this change-over switch stops at the fifthset of terminals and causes the connector circuit to be switched fromthe primary to the secondary operating magnet.

The calling'subscriber now operates his dial for the second digit, 0, ofthe called number, causing the apparatusto function as before exceptthat this time ten, instead of 2,impulses will be delivered to secondarymagnet SM because number 0 is pulled on the dial and because side switchwiper 52 is in second position. This circuit to magnet SM goes throughcontact 71 of relay BY so that. if the dial is again turned withoutreleasing on acall to a busy line, the connector switch wipers will notbe advanced, and a wrong connection made.

lVhen the second change-over is made, in the same way as the first, thechangeover switch wipers 41, 413 and 44: are left on the second pointand the side switch wipers 52, 65, 68,69 and are moved to the thirdposition when the following circuit is closed :ground GG, side switchwiper 68 and third position thereof, connector wiper 5'7, called lineterminal 72. sleeve trunk 73 to called line switch M, line switch wiper7%, terminal 75, winding 76 of cut off relay 0G to the source ofcurrent. This energizes the called line switch out off relay 0C, opensthe line switch battery bridge of the called line at contacts 77 and 78and closes the following circuit to ring the called partys bell :-commonA. C. generator GN, common interrupter INT, common lamp LP, winding ofgenerator cut off relay TR, side switch wiper 70 and third positionthereof, connector wiper 59 terminal 80, ring trunk 81 to called lineswitch M, called lineconductor S2, ringer 1" 2' at substation B, condenser 7c, impulse contact 83, contact 84 of relay 1), line conductor85, tip trunk 86 of called line switch, connector terminal 87,connect-or wiper 58, side switch wiper 69 and third position thereof,ground GH, through the battery and common resistance coil SE to theother side of the common generator GN. lVhen't-he side switchwipers wentto third position the following circuit was closed to energize theescape magnet ESCc-ground GF, off normal contact 66, contact 67 of relayBY, side switch wiper and third position thereof, winding 62 of magnetESQ, resistance coil RS to the source of current.

hen the called subscriber answers, a direct current path is closed atswitch hook contact 79 in the above traced circuit which causes relay TRto operate and close the following circuit :--ground GJ, contact 88 ofrelay TR, through resistance coil RS to battery. This short circuits theescape magnet winding 62, allowing it to release and advance the sideswitch wipers, 52, 65,68, 69 and 70 to the fourth position. Herethetalking current for the called party, fed through impedance coil AB, issubstituted for the ringing current above described, by side switchwipers 69 and 7 0 moving from the third to'the fourth positions. Thetalking battery for the calling substation transmitter is fed throughrelays T and R and thepath for the voice currents is through condensers105 and 106.3

After the conversation is completed the connection is released, by thehanging up of the receiver 1 at the calling substation A, in thefollowing manner :by opening the circuit at hool: switch contact 8,relays T and R at connector switch CN de-energize, Relay R, by closingits contact e8, causes the change-over switch CHO to move ,to' positionthree where the following circuit is closed :ground GD, contact 89 ofrelay T, terminal 90 and wiper 43 of .changeover switch CHO, winding ofrelay BL and contact 91thereof, common interrupter contact 92, commonresistance coil ES to the source of current. It may here be mentionedthat interrupters 121 and 122 are common to the exchange and are turnedin the. direction indicated by the arrows by the same shaft 113.Therefore when the above circuit is closed, the interrupter contact 92may or may not be closed, if not'closed noth ing will happen untilinterrupter 122 gets to the point where it causes the closure of contact92. When this circuit is completed, relay RL operates, locks by way ofits contact 95, and resistance coil SE, opens its energizing circuit atcontact 91 and closes its contact 94. Now, after a certain timeinterrupter 121 closes contact 93, this time being sufficient to inalresure that this is the release condition and not an impulse opening. Ifrelay RL was operated during impulsing, it would release beforeinterrupter 121 could close its contact and cause a release of'theswitch, because it would (lo-energize when relay T again energized andopened contact 89. When 121 interrupter contact 93 is closed, thefollowing circuit is established:ground GK, interrupter contact 93,contact. 94 of relay BL, contact 96 and winding 99 of connector releasemagnet REL to the source of current. This energizes the release magnetwhich locks from ground GL, low winding 1'00- and contact 102 of magnetREL, resistance coil RE to the source of current. The connector switchwipers and side switch wipers are now restored to normal when contact103 is opened. A circuit is also traced from ground GL, winding 100' andcontact 102 of magnet REL, connector trunk wire 38, terminal 104 andwiper lt of line switch L, winding 15 ofcut off relay CO tothe source ofcurrent. This circuit energizes the line switch out off re-.

1 lay CO and keeps the connector release magnet REL locked. A circuitmay now be traced from ground GL, winding 100 and contact 101 of magnetREL, connector trunk wire 83, terminal 32' and wiper 24 of line switchL,contact 25 of relay CO, contact, 28 and Winding 29 of line switchstepping magnet ST to the source of current, which causes the callingline switch L to take a step and go to its home point ready for use inagain selecting an idle connector. WVhen connector (1N restored itswipers to normal, the cut oflrelay, 0C of the called line switch M wasreleased. The following circuit is also closed to cause the release ofthe change-over switch CHO ground GD, terminals. 90, 114: and 115 ofswitch CHO, wiper 43 of switch'CHO, con-.

tacts 97; and 98 of connector release magnet REL, contact 12 and windingMO of switch CHO to the source of current. In multiple withthiscircuit'is winding 99 of magnet REL to the source of current. Thus theconnectorrelease magnet, upon energizing, will remain locked untilthe-connector shaft reaches normal, until the line switch L is releasedand until the change-ovei switch CHO is restored to normal, whereuponmagnet REL and relay R L are de-energized. llntil magnet REL isole-energized, ground GL, low winding 100 and contact 101 of magnet REL,is maintained in connection with multiple terminal 32 of all lineswitches in the group to keep thistrunkbusy.

A call to a busy line will now be described. Assuming that the samenumber, 20, was dialed and that, at the end of the second digit, theescape magnet ESC operates as before, relay R will be energized,relays'C and T will be (lo-energized and switch CHO will rest on point2. Escape magnet ESQ willnot release at this time because of thefollowing locking circuit :-ground on terminal 72, (placed there eitherfrom side switch wiper 6S and wiper 57 of some connector like CN whichhas called this same number or, if the subscriber having this number hasmade av call, a ground will be placed on terminal 72 in the same manneras was previously described for placing aground on terminal18 by lineswitch L} connector wiper 57 side switch 68 and second position thereof,contact 110 of relay BY, winding of relay BY, contact 108 of escapemagnet ESQ, winding 107 of magnet ESC to the source of current. Thiscircuit also causes relay BY to energize and lock itself in series withmagnet ESQ, holding them both, from ground GF, off normal contact 66,contact 109 of relay BY, winding of relay BY, contact 108 and winding107 of off, relay CO, calling line-conductor .2,-

through the substation apparatus A, line conductor 1, contact 9 of relayCO, line switch wiper 10 and contact 36, connector trunk wire 37,winding of relay B, through the battery to ground GE and then to theother side of busy induction coil BZ. This gives the calling subscribera tone which in dicates that the called forline is busy and when hehangs up his receiver, the connection is released inthe same manner aspre-* viously described.

From the above narrative it is apparent thatI have evolved a systemwherein neither primary impulse relays T and R need to be relativelyslow operating, or may both operate at the same speed or at slightlydifferent speeds, and in connection with such relays I have evolved asystem wherein the change-over function is, performed positively, andwherein the release of the switch is accomplished in a positive waywithout dependence being placed upon the co-operation of fast and slowrelays; also that this is accomplished in a system free from anynecessary grounds at the substations or third wire connectionethereto; afull use of a metallic talking circuitat the same time being had.

1am aware that numerous and extensive departures may be made from theembodiment of my invention illustrated and described but withoutdeparting from the spirit thereof. -For instance, I am aware that otherequivalent means may be provided for many of theelements hereinspecifically discussed, but what I claim as my invention is defined inthe following claims 1. In a telephone system, the combination withaplurality of substations, a main station, switching mechanism at themain station adapted to make connection with a desired calledsubstation, line conductors connecting the said switching mechanism anda calling substation, a circuit interrupter at the substation and asource of current associated with the said, switching mechanism, meansto cause the said circuit interrupter to interrupt the circuit of theline conductors a definite, predetermined number of times, meansoperative upon the subsequent closure of thesaidline conductors by thesaid interrupter to interpose a high resistance in said circuit, a pairof relays for controlling the said. switching mechanism under thecontrol of the said c rcuit lnterrupter,

each of the said relays being responsive to circuit closures with normalcurrent flowing over the line conductors, and only one 01' thev saidrelays being responsive to the closure of the said line conductorsthrough the said resistance.

2. In a telephone system, the combination with a plurality ofsubstations, a. main sta tion, switching mechanism at the main stationadapted to make connection with a desired called substation, lineconductors connecting the said switching mechanism and a callingsubstation, a circuit interrupter at the substation and a source ofcurrent associated. with the said switchingv mechanism, means to causethe said. circuit interrupter to interrupt the circuit oi the lineconductors a definite predetermined number of times. means operativeupon a subsequent closure of the saidline conductors by the said interru'iter to interpose a high resistance in said circuit, a pair of relaysfor controlling the said switching mechanism under the control of thesaid circuit interrupter, each of the said relays being" responsive tocircuit closures with normal. current flowing over the'lineconductors,and only one of the said relays being resoonsive to theclosure of the saidv line conductors through the said re sistance, andchange-oven switching means adapted to be operated under thejointcontrol oi the said pair of: relays when one of the said pair isoperated and the other relay is quiescent.

3. In a telephone system, the combination with a plurality ofsubstations, a main station, switching mechanism at the main stationadapted to make connection with a desired called substation, lineconductors connecting the said switching mechanism and a callingsubstation, a circuit interrupter at the substation and a source ofcurrent as sociated with the said switching mechanism, means to causethe said circuit interrupter to interrupt the circuit of the lineconductors a definite predetermined number of times, means operativeupon a subsequent closure of the said line conductors by the saidinterrupter to inter-pose a high resistance in said circuit, a pair ofrelays for controlling the said switching;- mechanism under the controlof the said circuit interrupter, each of the said relays being responsive to circuit closures with normal current flowing over the lineconductors, and only one of the said relays being responsive to theclosure of the said line conductors through the said resistance.change-over? switching means adapted to be operated under the jointcontrol of the said pair of re lays when one of the said pair isoperated and the other relay is quiescent and means to prevent theoperation of: the said changeover switching means when both of the saidrelays are operated.

i. In an automatic telephone systcm,'the combination with telephonelines, substations for the lines, a main station wherein the linesterminate,switching mechanism at the main station, means to interlinlr acalling line with the said switching mechanism, a pair oi relayscontrolling the said switching mechanism under the control of callingsubstation apparatus, a circuit interrupter at the substation, means tovariably operate the said circuit interrupter to interrupt the circuitor the calling line a predetermined number of times, means to include aresistance in circuit withthe said line after the end of each series ofcircuit interruptions, a source of current, and circuit connections tocause the operation of each of the said relays at each normal closure ofthe line circuit, one of the said relays being irresponsive to the saidclosure through the said resistance.

5. in a telephone system, the combination with a plurality ofsubstations, a main station, switching mechanism at the main stationadapted to maize connection with 'a desired *alled substation, lineconductors connecting the said switching; mechanism and a callingsubstation, a circuit interrupter at the substationand a source ofcurrent associated with the said switching mechanism, means to arisethe'said circuit interrupter to interrupt the circuit of the lineconductors a definite predetermined number of times, means operativeupon a subsequent closure of the said line conductors by the saidinterrupter to interpose a high resistance in said circuit, a pair ofrelays for controlling the said switching mechanism underthe control ofthe said circuit interrupter, each of the said relays being" responsiveto circuit closures with normal current flowing over the lineconductors, and only one of the said relays being responsive to theclosure of the said line conductors through the said resistance,changeover switching means adapted to be operated underthe jointcontrol. of the said pair of relays when one of the said pair isoperated and the other relay is quiescent, locking means for the saidresistance interposing means at the substation, and unlockmeans for thesaid locking means under the control of the said change-owl switchingmeans.

6. In a telephone system, the combination with a plurality ofsubstations, a main station, switching mechanism at the main stationadapted to make connection with a desi d 'callcd substation, lineconductors conhearing the said switching mechanism and a callingsubstation, a circuit interrupter at the substation and a source ofcurrent associated with the said switching mechanism, means to cause thesaid circuit interrupter to interrupt the circuit of the line conductorsa definite predetermined number of control of the said pair of relayswhen one oi? ,ing means.

' the said pair is operated and the other relay is-quiescent, means toprevent the operation oi? the'said change-over switching means when bothoi the said relays are operated,

locking means for the said resistance inter- 20 posing means at thesubstation, and unlocking means for the said lockingmeans under thecontrol of the said change-over? switch- 7. In an automatic telephonesystem, the combination with telephone lines, substations for the lines,a main station wherein the lines terminate, switching mechanism at themain station, means to interlink a calling line with the said switchingmechanism, a pair of relays controlling the said switching mechanismunder the control of calling srnstationapparatus, a circuit interrupterat the substation, means to variably operate the said circuitinterrupter to interruptthe circuit of the calling line a predeterminednumber of times, means to include a resistance in circuit with the saidline after the end oi each series 01 circuit interruptions, a source ofcurrent, circuit connections to cause the operation ot' each of the saidre- 2 at each normal closure of the line cir- 'cuit, one of the saidrelays being iii-responsive to the said closure through thesaid'resistanco, and changebvcr switching means adapted to be operatedunder the joint control ot' the said pair Oil relays, when one of thesaid pair is operated and the other is quiescent.

In an autoi'nat-ic telephone system, the combination with telephonelines, substations for the lines, a main station wherein the linesterminate, switching mechanism at the main station, means to interlink acall- .ing line with the said switching mechanism, a pair of relayscontrolling the saidswitchins: mechanism under the control olicallingsubstation apparatus, a circuit interrupter at the substation, means'tovariably operate the said .circuit interrupter to interrupt the (in cultof the calling line a predetermined numher of times, means to include aresistance in circuit with the said line after the end of each seriesoil circuit interruptions, source of current, circuit connections tocause the operation'ot each of the said relays ateach normal closure oftheline circuit, one of the said relays beingirresponsive to the saidclosure through the said resistance, changeover switching means adaptedto be operated under the joint control'of the said pair of relays, whenone of the said pair'is' operated and the other is quiescent, and meansto prevent the operation of the said -change-ove1 switching means whileboth of the said relays are operated.

9. In an automatic telephone system, the combination with telephonelines, substa tions for the lines, a main station wherein the linesterminate, switching mechanism at the mainstation, means to interlink acall-' 111;); line with the said switchlng mechamsm,

tions to cause the operation of each of the.

said relays at each normal closure of the line circuit, one of the saidrelays being irresponsi-ve to the said closure through the saidresistance, change-over swltchlng means adapted to be operated underthe.

joint control of the said pair of relays when one of the said pair isoperated and the other is quiescent, locking means for the saidresistance interposing means"at the substation, and unlocking means forthe said locking means under the control ofthe said change-overswitching means. V

10. In. an automatic telephone system,the combination with telephonelines, substations for the lines, a main station wherein the linesterminate, switching mechanism at the main station, means to interlink acalling line with the said switching mechanism, a pair of relayscontrolling the said switching mechanism, under the control of callingsubstation apparatus, a circuit interrupter at the substation, means tovariably operate the said circuit interrupter to'interru pt the circuitof the calling line a predetermined number of times, means to includearesistance in circuit with the said line after the end of each seriesof circuit interruptions, a source of current, circuit connections tocause the operation of each of the said relays at each normal closure ofthe line circuit, one of the said relays being irresponsive to the saidclosure through the said resistance, change-over switching means adaptedto'be operated under the joint control oi the said pair of relays, whenone of the said pair is operated and the other is quiescent, means toprevent the operation of the said change-over switching means while bothof the ,said relays are operated, locking means for the said resistanceinterposing means at thesubstation, and unlocking means for the saidlocking means under the control of the said change-overswitching means.I I

11. In an automatic telephone system, the combination with telephonelines, substations for the lines, a main station wherein the linesterminate, switching mechanism at the main station, means to interlink acalling line with the said switching mechanism, a pair of relaysdirectively controlling the said switching mechanism under the controlof calling substation apparatus, including a substation circuitinterrupter, means to variably operate the said circuit interrupter toproduce successive series of calling line circuit interruptions, meansincluding an elec tromagnet to include a resistance in series with thesaid line immediatelyv following each series of circuit interruptions, asource of current, and circuit connections to cause the operation ofeach of the said relays at each normal closure of the line circuit, oneof the said relays being irresponsive to the final closure after thelast circuit interruption or each series through the said resistance.

12. In an automatic telephone system,the combination with telephonelines, substations for the lines, a main station wherein the linesterminate, switching mechanism at the main station, vmeans to interlinka calling line with the said switching mechanism, a pair of relaysdire'ctively controllingthe said switching mechanism under the control,

of calling substationapparatus, including a substation circuitinterrupter, means to variably operate the said circuit interrupter to:

produce successive series of calling line circuit interruptions, meanslncludlng an electromagnet to include a resistance-in series.

with the said line immediately following each series of circuitinterruptions, a source of current, circuit connections to. cause-theoperation of each of the said relays at each normal closure of the linecircuit, one of the said relays being irresponsive to the. final closureafter the last circuit interruption of each series through the saidresistance, and

change-over switching controlling means adapted to be operated under thejoint control of the said pair of relays when one of the said pair isoperated and the other relay is quiescent. v

'13. In an automatic telephone system, the combination with telephonelines, substations for the lines, main station wherein the linesterminate, switching mechanism at the main station, means to interlink acalling line with the said switching mechanism, a pair of relaysdirectively controlling the said switching mechanism under the controlof calling substation apparatus, including a substation circuitinterrupter,

means to variably operate the said circuit interrupter to producesuccessive series of calling line circuit interruptions, means includingan electromagnet to include a resistance in series with the said lineimmediately following each series of circuit in terruptions, a source ofcurrent, circuit connections to cause the operation of each of the saidrelays ateach normal closure of the line circuit, one of the said relaysbeing irresponsive to the final closure after the last circuitinterruption of-each series through the. said resistance, change-overswitching controlling means adapted to be operated under the jointcontrol of the said pair of relays when one of the said pair is operatedand the other relay is quiescent, a locking circuit for the saidelectromagnetic resistance including means, means to maintainthesaidlocking circuit operative under the control of the said electromagnetafter an initial operation thereof, and circuit unlocking meansresponsive to the complete operation of the said change-over means tounlock the said circuit to disable the said resistance including means.

14;. In an automatic telephone system, the combination with telephonelines, substations ior the lines, a main station wherein the linesterminate, switching mechanism at the main station, means to interlink acalling line with the said switching mechanism, a pair of relaysdirectively controlling the said switching mechanism under the controlof calling substation apparatus, including a substation circuitinterrupter, means to variably operate the said circuit interrupter toproduce successive seriesv of calling line cir cuit interruptions, meansincluding an e1ectromagnet to include a resistance inseries with thesaid line immediately following each series of circuit interruptions,asource of current, circuit connections to cause the Operation of eachof the said relays at each normal closure of the line circuit, one ofthesaid relays being irresponsive to the final closure after the lastcircuit interruption of each series through the said resistance,change-over, switching controlling means adapted to be operated underthe joint control of the said pair of relays when one of the said pairis operated and the other relay is quiescent, and means to prevent theoperation of the said change-over switching means during the periodwherein at any time both of the said relays are operated.

15. In an automatic telephone system, the combination with telephonelines, substations for the lines, a main stationwherein the linesterminate, switching mechanism at themain station, means to interlink acalling line with the said switching mechanism, a pair of relaysdirectively controlling the said switching mechanism under the controlof calling substation apparatus, including a substation circuitinterrupter, means to vari-f ably operate the said circuit interrupterto produce successive series of call ng line 011'- cuit interruptions,means including an electromagnet to include a resistance in series withthe said'line immediate following each series of circuit interruptions,a source of current, circuit connections to cause the operation of eachof the said-relays at each normal closure of the line circuit, one ofthe said relays'being' irresponsive to the final closure after the lastcircuit interruptionof each series through the said resistance,changeover switching controlling means adapted to' be operated under thejoint control of the said pair of relays when one of the said pair isoperated and the other relay is quiescent, meansto prevent theop'erationof thesaid change over switching means during'the period wherein at anytime both of the said relays areoperated, a locking circuit for the saidelectromagnetic resistance including means, means to maintain the saidlocking circuit operative under the control of the said electromagnetafter an initial operation thereof, and circuit'unlocking meansresponsive to the complete operation of the said change-over"means tounlock the said circuit to disable the said resistance including means.

16. In an automatic telephone system, the combination with telephonelines, substations for the lines, a main station wherein the linesterminate, an automatic numerical switch at the main station,anon-numerical switch to interlin'k a callingline with the sa1dnumerical switch, a pair of relays for the said numerical switch, meansat the sub-'- station toiproduce successive series of circuitinterruptions, means at the substation to operate both of the said pairof relays substantially in unison during each circuit interruption of aseries, substation controlling means for differently operating therelays for a period immediately following the-last circuit interruptionof a series, a plurality of operating magnets for the said numericalswitch, one of which is operative under said substation control to movethe switch in a primary direction during a first series of circuitinterruptions, a second of which is operative to be moved in a secondarydirection during a second series of circuit interruptions, change-overmeans to'remove the primary 5 operating magnet from the control of thesaid pair of relays and to place the secondary operating magnet underthe control of the said pair of relays, and means to cause the operationof the said change-over means responsive to the differently operatedpair of relays under the control of thesaidsubstation controlling means.

17. In an automatic telephone system, the combination with telephonelines, substations for the lines, a main station wherein the linesterminate, an automatic numerical switch at the main station, anon-numerical switch-to interlink a calling line- -vvith the saidnumerical switch, a pair of relays for the said numerical switch, meansat the substation to produce successive series of circuitinterruptions,- means at the substation to operate both of the said pairof relays substantially in unison during each circuit interruption ofaseries, substation controlling means for differently and continuously.operating the relays for a period immediately following the last circuitinterruption of a. series, a plurality of operating magnets for the saidnumerical switch, one of which is operative under substation control tomove the switch in a primary direction during the first series ofcircuit interruptions, a second of which is operative to-move theswitchlin a secondary direction during a second series of circuitinterruptions, change-over means to remove the primary operating magnetfromthe control of the said pair of relays and to place the secondaryoperating magnetunder the control of the said pairof relays, means tocause the operation. of the said change-over" means responsive to thecondition of the differently operated pair of relays resulting from thecontrol of the said substation controlling means, and separatecontrolling means for the said numerical switch to prevent improperoperationof the said switch due to differing response rates forthe saidrelays to circuit interruptions.

18. In'an automatic" telephone system, the. combination with telephonelines, substations for the lines, a main station wherein the linesterminate, an automatic numerical switch at themain station, anon-numerical switch to interlink a calling line with thesaid numericalswitch, a pair of relays for, the said numerical switch, means at thesubstation to produce successive series of circuit interruptions, meansat the'substation to operate .both of .the said pairof relayssubstantially in unison during each circuit interruption of a series,substation controlling means for differently and continuously operatingthe relays for a period immediately,following the last circuitinterruption of a series, a plu-, rality of operating magnets for" thesaid numerical switch, one of which is operative under substationcontrol to move the switch in a primary direction during thefirst'series of circuit interruptions, a second of which is operative tomovethe switch in a secondary direction during a second series ofcircuit interruptions, changeover means to remove the primaryoperating'magnet from the control of the said pair of relays andto'place the secondary operating magnet under the controlof the saidpair of relays, means to cause the operation of the said changeovermeans responsive to the condition of the differently operated pair ofrelays resulting from the control of the saidsubstation controllingmeans, and separate controlling means tor'the said numerical switch toprevent improper operation of the said changeover means due to differingresponse rates for the said relays to circuit interruptions.

19. In an automatic telephone system, the combination with telephonelines, substations for the lines, a main station wherein the linesterminate, an automatic numerical switch at the main station, circuitconnections interlinking a calling linewvith the said numerical switch,a pair of relays for the said numerical switch, means at the substationto produce successive series of circuit interruptions, means at thesubstation to operate both of the said pairof relays substantially inunison during each circuit interruption of a series, substationcontrolling means for differently and continuously operating the, relaysfor a period immediately following the last circuit interruption of aseries, a plurality of operating magnets for the said numerical switch,one of which is operative under substation control to move the switch ina primary direction during the first series of circuit interruptions, asecond of which is operative to move the switch in a secondary directionduring a second series of circuit interruptions, change-over means toremove the primary operating magnet from the control of the said pair ofrelays and to place the secondary operating magnet under the control ofthe said pair of relays, means to cause the operation of the saidchangeover *means responsive to the condition of the differentlyoperated pair of relays resulting from the control of the saidsubstation controlling means, and correcting means under the jointcontrol of the said pair of relays to prevent the improper operation ofthe said change-over means or" the said numerical switch, due to thesaid relays operating at different rates of speed. 20. In an automatictelephone system, the combination with telephone lines, substations forthe lines, a main station wherein the lines terminate, an automaticnumerical switch at the main station, circuit connections interlinking acalling line with the said numerical switch, a pair of relays for thesaid numerical switch, means at the substation to produce successiveseries of circuit interruptions, means at the substation to operatebothof the said pair of relays substantially in unison during each circuitinterruption of a series, substation controlling means for differentlyand continuously operating the relays for a period immediately followingthe last circuit interruption of a series, a plurality of operatingmagnets for the said numerical switch, one of which is operative undersubstation control to move the switch in a primary direction during illthe first series of circuit interruptions, a second of which isoperative to move the switch in a secondary direction during a secondseries of circuit interruptions, change-over means to remove the primaryoperating magnet from the control of the said pair of relays and toplace the secondary operating magnet under the control of the said pairof relays, means to cause the operation of the said change-over means.responsive tothe condition ofthe differently operated pair of relaysresulting from the control of the said substation controlling means, astep-by-step switch for the said numerical switch operating under thecontrol of one of the said relays in response to the said circuitinterruptions and circuit connections jointly controlled by the saidpair of relays, and contacts of the said stepby-step switch to preventimproper operation of the said changeover means on account of the slightdifferences in the speeds of action or release between the said relaysin response to the said circuit interruptions.

21. In a telephone system, the combination with a plurality of telephonelines, substations for the lines, a main station, a selective switch atthe main station adapted to interconnect two of the said telephonelines, a source of current, a relay in the circuit of the said source ofcurrent leading to a substation of a connected line, a release magnet, arelease relay, a timing mechanism, a pair of circuits successively controlled thereby, there being a predetermined interval between thecontrol exercised by the said timing mechanism on the one circuit andthe control exercised by the said timing mechanism upon the secondcircuit, circuit connections to include in the said first circuit a.winding of the said release relay, a SOUTCG'OTf current, contacts of thesaid substation circuit relay and controlling contacts of the saidtiming mechanism, circuit connections for the second circuit comprisinga winding of the said release magnet, contacts of the said releaserelay, and controlling contacts of the said timing mechanism.

22. Inan automatic telephone system an automatic selective switch forinterconnecting telephone line substations, a telephone line substationcontrolled relay, a release magnet for the said switch, a release relay,a

pair of continuously successively operating controlling sets ofcontacts, a circuit for the said release relay comprising a firstoperated set of controlling contacts and contacts of said substationcontrolled relay, and a circuit for said release magnet comprising saidsecond operated set of controlling contacts and contacts oi the saidrelease relay.

In an automatic telephone system, the combination with an automaticselective switch for interconnecting telephone line substations,a'telephone line substation controlled relay, a release magnet tor thesaid switch, a release relay, a pair of continuously successivelyoperating controlling sets ofcontacts, a circuit for the said releaserelay comprising a first operated set of controlling contacts andcontacts of said substation controlled relay,'a circuit for said releasemagnetcomprising said second operated set of controlling contacts. andcontacts of the said released-clay, and a locking circuit for the saidrelease relay under the control of oii normal contacts ofthe saidswitch.

2%. In an automatic telephone system, an automatic selective switch forinterconnecting telephone line substations, a telephone line substationcontrolled relay, a release magnet for the said switch, a release relay,a pair of continuously successively operating controlling sets ofcontacts, a circuit for the said release relay comprising a firstoperated set of controlling contacts and contacts of said substationcontrolled relay, a circuit for said release magnet comprising saidsecond operated set of controlling contacts and contacts of the saidrelease relay, and other automatic selective switches forinterconnecting other pairs of telephone lines, said pair of sets ofcontrolling contacts being common to all of the said automatic selectiveswitches. p

25. In an automatic telephone system, the combination with an automaticselective switch for interconnecting telephone line substations, atelephone line substation controlled relay, a release magnet for thesaid switch, a release relay, a pair of continu-' ously successivelyoperating controlling sets of contacts, a circuit for the said releaserelay comprising a firstoperated set of con trolling contacts andcontacts of said substation controlled relay, a circuit for said releasemagnet comprising said second operated set of controlling contacts andcontacts ofthe said release relay, a locking circuit "for the saidrelease relay under the control of oil normal contacts of the saidswitch and other automatic selective switches for.

tacts being common to all of thejsaid automatic' selective switches.

26. In a telephone system, telephone lines,"

substations on. the lines, automatic switch- 111g mechanism forinterconnecting a pair of the telephone lines, a calling substationcontrolled relay, means to'release the said relay when the callingsubstation is retired,

two sets of controlling contacts adapted to be successively operatedwith a definite time interval between the operation of the first set andthe operation of the second set, a winding of a release relay, the firstset of contacts and normal contacts of the said calling substationcontrolled relay in a first circuit, said second set of contacts,normally,

open contacts oi"v said release relay and a winding o1 a release magnetin asecond circuit, said first circuit controllingthe said secondcircuit to operate the said release magnet, and means including offnormal contacts ofthe said switching mechanism under the control of thesaid release magnet for controlling the said release relay.

2?.) In a telephone system, telephone lines, substations for the lines,automatic switching mechanism for interconnecting a pair of thetelephone lines, a calling substation controlled relay, means to releasethe said relay when the callingsubstation is retired, two sets ofcontrolling contacts adapted to be successively operated with a definitetime interval between the operation of the first set and theoperationofthe second set, a winding oi a release relay, the first setof contacts and normal contacts of the said calling substationcontrolled relay in a first circuit, said second set of contactsnormally open contacts of said relay. and a winding of a release magnetina second circuit, said first circuit controlling the said secondcircuit to operate the said release magnet, means including off normalcontacts of the said switching mechanism under the control of the saidrelease relay-for controlling the said release magnet, and" otherswitching mechanisms each-having a substation controlled relay, .releaserelays and release magnets individual to each, but said time controllingcontacts being common -to all.

28. In a subscriber operated telephone system, the combination withtelephone lines, substations for the subscribers on each of the lines, aplurality of switches at a'main station,'each adapted to interconnecttwo of the said lines, a substation controlled relay for each switchunder the control of substation apparatus oi: a calling line,normally'closed and normally open contacts for the said relay, 'a sourceof current, a release relay, offnormal contacts of the said switch.- apair of 'controlling'contacts in the circuit of the normal contacts ofthe said relay, a second pair of controlling contacts, controllingcontact operating means adapted to continuously and successively'operatethe said first named pair of controlling contacts and thesecond namedpair of controlling contacts, a locking circuit for the said releaserelay adapted to operatively lock the said release relay whenever thesaid release relay is operated by the closure of the said firstnam'edpair of controllingcontacts said locking circuit also being under thecontrol of normal contacts of the substation controlled relay, a releasemagnet for the said switch, a winding therefor and a circuit for thesaid winding including a source of current, normally open contacts ofthe said release relay-and the second operated pair of controllingcont-acts to operate the said release relay.

29. In a subscriber operated telephone system, the combination withtelephone lines, substations for the subscribers on each of the lines, aplurality of switches at a main station, each adapted to interconnecttwo of the said lines, a substation controlled relay for each switchunder the control of substa tion apparatus or a calling line, normallyclosed and normally open contacts for the said relay, a source ofcurrent, a release relay, off normal contacts of the said switch, a pairof controlling contacts in the circuit of the normal contacts of thesaid relay, a second pair of controlling contacts, controlling contactoperating means adapted to con tinuously and successively operate thesaid first named pair of controlling contacts and the second named pairof controlling contacts, a locking circuit for the said release relayadapted to operatively'lock the said release relay whenever the saidrelease relay is operated by the closureot thesaid first named pair ofcontrolling contacts, said loclring circuit also being under the controlor" normal contacts of the substation controlled relay, a release magnetfor the said switch, a winding therefor and a circuit for the saidwinding including a source of current, nor

mally open contacts of the said release relay and the said secondoperated pair of controlling contacts to operate the said releasemagnet, and a locking circuit for the said release magnet including 0Enormal contacts of the said switch.

30. In a subscriber operated telephone system, the combination withtelephone lines, substations for the subscribers on each of the lines, aplurality of switches at a main station, each adapted to interconnecttwo of the said lines, a substation controlled relay for each switchunder the control of substation apparatus of a calling line, normallyclosed and normally open contacts for the said relay, a source ofcurrent, a release relay, off normal contacts of the said switch, a pairof controlling contacts in the circuit of the normal contacts of thesaid relay, a sec- 0nd pair of controlling contacts, controlling contactoperating means adapted to continuously and'successively operate thesaid firstnamed pair of controlling contacts and the second-named pairof controlling contacts, a locking circuit for the said release relayadapted to operatively lock the said release relay whenever the'saidrelease relay is operated by the closure of the said first-named pair ofcontrolling contacts, said locking circuit also being under the controlof normal contacts of the substation controlled relay, a release magnetfor the said switch, a winding therefor and a circuit for the said winding including a source of current, normally opencontacts ol the saidrelease relay and the said second operated pair of controlling contactsto operate the said release relay, a locking circuit for the saidrelease magnet including off normal contacts of the said switch, both ofsa-idpairs of controlling contacts being common to a plurality of thesaid switches.

31. In a subscriber. operated telephone system, the combination withtelephone lines, substations tor the subscribers on each of the lines, aplurality of switches at a main'station, each adapted .to interconnecttwo of the said lines, a substation controlled relay for each switchunder the control. or substation apparatus of a calling line, normallyclosed and normally open contacts for the said relay, a source ofcurrent, a release relay, off normal contacts of the said switch, a pairof controlling contacts in the circuit of the normal contacts of thesaid relay, a second pair of controlling contacts, controlling contactoperating means adapted to continuously and successively operate thesaid first named pair of controlling contacts and the second-named pairot'controlling contacts, a locking circuit for the said release relayadapted to operatively lock the said release relay whenever the saidrelease relay is operated by the closure of the said first-named pair ofcontrolling contacts, said locking circuit also being under the controlof normal contacts of the substation controlled relay, a release magnetfor the said switch, a winding therefor and a circuit for the saidwinding including a source of current, normally open contacts of thesaid release relay and the second operated pair of controlling contactsto operate the said release magnet, said controlling contact operatingmeans being common to a plurality of the said switches.

32. In a subscriber operated telephone system, the combination withtelephone lines, substations for the subscribers on each of the lines, aplurality of switches at a main station, each adapted to interconnecttwo of the said lines, a substation controlled relay for each switchunder the control of substation apparatus of a calling line, normallyclosed and normally open contacts for the said relay, a source ofcurrent, a release relay olf normal contacts of the said switch, a pairof controlling'contacts in the circuit of the normal contacts of thesaid relay, a second pair of controlling contacts, controlling contactoperating'means adapted to continuously and successively operate thesaid firstnamed pair of controlling contacts and the second-named. pairof controlling contacts, a locking circuit for the said release relayadapted to operatively lock the said release relay whenever the said,release relay is operated by the closure of the said first-named pair ofcontrolling contacts,

said locking circuit also being under the control oi normal contacts orthe substation controlled relay, a release magnet for the said switch, awinding therefor and a circuit for the said winding including a sourceof current, normally open contacts of thesaid release relay and the saidsecond operated pair of controlling contacts to operate the said releasemagnet, a locking circuit for the said release magnet including oilnormal contacts out the said switch, both of the said pairs ofcontrolling contacts being common to a plurality of the said switches. I

In a subscriber operated telephone system, the combination withtelephone lines, substations for the subscribers of each of the lines, aplurality of switches at a main station, each adapted tointerconnect twoof the said lines, a substation controlled relay for each switch underthe control of substation apparatus ofa calling line, normally closedand normally opencontacts for the said relay, a source of current, arelease relay, of? normal contacts of the said switch, a pair ofcontrolling contacts in the circuit of the normal contacts of the saidrelay, a second pair of controlling contacts, controlling contactoperatingmeans adapted to continuously and successively 0P? crate thesaid first-named pair of controlling contacts and the second named pairof controlling contacts, a locking circuit for the said release relayadapted to operatively lock the said release relay whenever the saidrelease relay is operated by the closure of the said first-named pair ofcontrolling contacts, said locking circuit also being under the controlof normal contacts of the substation controlled relay, a release magnetfor the said switch, a windingtherefor and a circuit for the saidwinding including a source of current, normally open contacts of thesaid release relay and the said second operated pair of controllingcontacts to op erate the said release" magnet, a locking circuit for thesaid release magnet including oil normal contacts of the said switch,both of the said pairs of controlling contacts being under the controlof common control contact actuating means for a plurality of saidswitches.

34. In a telephone system, incoming circuits, a plurality of outgoingcircuits, means including directively controlled automatic switches forinterconnecting said incoming circuits with any of said outgoingcircuits, acontrolling circuit for'each switch'including two sides of anincoming circuit in series, each switch being advanced in responsetomomentary interruptions of its controlling circuit and arranged to bereleased in response to a long interruption of its controlling circuit,and a mechanical device common to a plurality of said switches forpreventing the release of any of saidautomatic switches during momentaryinterruptions of its controlling circuit.

35. In a telephone system, an incoming line, a plurality of outgoing:lines, an automatic switch for interconnecting said incoming line withany of said. outgoing lines, a controlling circuit for. said switchincluding two sides of said incoming line in series, said switch beingadvanced in response to momentary interruptions of said controllingcircuit and arranged to be released in response to a long inter--ruption of its controlling circuit, and a constantly'operating devicefor preventing the release of said automatic switch during momentaryinterruptions of its controlling. circuit.

36. In atelephone system, an incoming line, a plurality of outgoinglines, an auto.- matic switch for interconnecting said incoming linewith any of said outgoing lines, a controllingcircuit for said switchincluding. two sides of said incoming line in series, said switch beingadvanced in response to momentary interruptions of said controllingcircuit and arranged to be released in response to a long interruptionof its controlling circuit, and a constantly rotating device forpreventing the release oi said automatic switch during momentaryint'erruptionsof its controlling circuit.

T 37.-In a telephone system, an incoming line, a plurality of outgoinglines, an automatic switch forinterconnectingsaid incoming line with anyof said outgoing lines, a controlling circuit for said switch I in:cluding two sides of said incoming line in series, said switch beingadvanced in response to momentaryinterruptions of said controllingcircuit and arranged to be released in. response to a longinterruption-of its controlling circuit, and a uni-directional rotarycircuitclosing switch for preventing the release of said automaticswitch during momentary interruptions of its controlling circuit. v

38. In a telephone system, an incoming line, a plurality of outgoinglines, an automatic switch for interconnecting said incoming line withany of said outgoing lines,

a controlling circuit'for said switch includ-- ing two sides ofsaidincoming line in series, said switch beingadvanced in response tomomentary interruptions of said-controlling circuit and arranged to bereleased in response toalong interruption of its controlling circuit,and a constantly rotating interrupting device for preventing the releaseof said automatic switch during momentary interruptions of itscontrolling circuit.

39. In a telephone system, an incoming line, a plurality of outgoinglines, an automatic switch for interconnecting said incoming line, withany of said outgoingvlines, a

telephone line circuit, a cut-off relay associated with each telephoneline circuit and controlled over a selected trunk circuit to disconnectsaid line relay from its associated line during conversation and tore-connect said line relay to said telephone line at the close ofconversation, releasing means for said non-numerical switch, a timingdevice common to a plurality of non-numerical switches and meansincluding said timing device and a cut-off relay for operating saidreleasing means.

In testimony whereof, I hereunto subscribe my name this 22nd day of Jan,A. D. 1919.

- lVINFEED T. PO /VELLQ

